Invasion of the respiratory tract is a common route for microbes to establish infection.
Certain types of individuals are prone to respiratory infection (e.g., by bacteria (e.g., opportunistic bacteria), viruses, fungi and/or parasites) including the immunocompromised, elderly, cancer chemotherapy patients, individuals suffering from asthma, individual suffering from genetically inherited disease (e.g., cystic fibrosis) and virally infected individuals (e.g., infected with influenza virus, respiratory syncytial virus (RSV), adenovirus and/or human immunodeficiency virus).
A serious consequence of cystic fibrosis (CF) is Pseudomonas aeruginosa lung infection, which by itself accounts for almost 90% of the morbidity and mortality in CF (See e.g., Cystic Fibrosis Foundation. Patient Registry 1994 annual data report, Bethesda, Md. 1995). By age 12, 60-90% of CF patients are infected with P. aeruginosa, and most die before age 30. Pathogens such as Staphylococcus aureus and nontypable H. influenza are also commonly isolated from the respiratory tract of CF patients. Progressive loss of pulmonary function over many years due to chronic infection with mucoid P. aeruginosa is the hallmark of CF.
Asthma is a disorder of the respiratory system characterized by airway hyperresponsiveness leading to acute and/or chronic airway inflammation. The severity of hyperreactivity typically correlates with the degree of inflammation. Mucus hyper-secretion and mucus cell hyperplasia are seen in the lungs of patients with asthma. In chronic asthmatic individuals, mucus forms a viscoelastic gel, which is very sticky. When it stagnates, mucus can occlude the airway and become a favorable locus for bacteria or disease pathogenesis.